Residents should be bracing for rainfall beginning Wednesday morning, Environment Canada said.

The department has issued a special weather statement for Hamilton, Niagara and much of central Ontario Tuesday afternoon, as a low pressure system is expected to affect the region beginning Wednesday morning and continuing Thursday.

The system will bring rain — heavy at times — and isolated thunderstorms, Environment Canada says.

The slow moving nature of the system may result in significant rainfall between 30 to 40 millimetres, with higher amounts possible in thunderstorms.